Secondary containment for liquid

ABSTRACT

In secondary containment of a liquid in a tank which has pipes or posts extending into the ground, a liner covering the ground within a containment wall has a hole surrounding each pipe. Each hole is sealed by a boot which surrounds the pipe and connects from the pipe to the liner and includes a sleeve portion clamped to the pipe and a flange surrounding the sleeve portion at one end which is welded to the liner. A frusto-conical or accordion shape expandable portion is provided allowing longitudinal movement of the flange relative to an upper part of the sleeve of the boot such that the expandable portion allows the liner lies to move downwardly relative to the pipe. The expandable portion is of larger diameter than at the upper part of the sleeve so as to allow the flange to move horizontally with the liner relative to the member.

This invention relates to a secondary containment system for liquidstorage and transfer systems which include generally tanks and the likewhich includes a containment wall surrounding the system and a linercovering the ground surrounding the system up to the containment wall sothat any escaping liquid from the system is contained to prevent groundcontamination.

BACKGROUND OF THE INVENTION

Examples of secondary containments systems of this general type areshown in U.S. Pat. Nos. 5,800,091 (Van Romer) issued Sep. 1, 1998,5,882,142 (Siglin) issued Mar. 16, 1999 and 4,765,775 (Kroger) issuedAug. 23, 1988. In each of these a containment wall is suitably supportedand receives a liner which extends across the ground to an outer edgewhich is sealed to the wall at a height part way or wholly up the wallso that the liquid escaping from the tank either gradually orcatastrophically is contained.

In Siglin and Kroger, it appears that the tank is merely located restingupon a fill material inside the wall and on top of the liner. In VanRomer the tank appears to be standing on legs with base plates restingon the liner.

In practice this support of the tank is not suitable and commonly thetank is supported on pilings extending into the ground in the areainside the containment wall. Also there may be pipes from the tank whichextend into the ground at the area within the containment wall. Thus theliner must be perforated at these locations so that the elementconcerned passes through the liner.

Pipe boots in the form of a cylindrical sleeve with a disk attached atone end are commonly used to form a seal between the pipe pilings, orother penetrating member, and the secondary containment liners that areused to contain spills. One end of the boot is clamped to the pipe by asurrounding clamp and the other is welded to the liner.

Material used in the pipe boots is similar to the liner material andexhibits the same properties. The most important feature iscompatibility with the contained product, and the ability to be sealedto the liner and the penetrating member such as the piling. Themanufacturing process must be capable of maintaining a minimumthickness, as this is often specified by governing bodies. As a resultof this requirement, specialized manufacturing procedures must beutilized.

SUMMARY OF THE INVENTION

It is one object of the invention to provide a pipe boot of an improvedconstruction.

According to one aspect of the invention there is provided a method forsecondary containment of a liquid in a liquid container, where theliquid container is surrounded by a containment wall and where theliquid container has connected thereto at least one member which extendsfrom the liquid container downwardly into the ground within thecontainment wall the method comprising:

providing a liner covering the ground within the containment wall andextending from the containment wall at least partly under the liquidcontainer;

forming in the liner a hole surrounding the member;

providing a boot which surrounds the member and connects from the memberto the material of the liner surrounding the hole;

providing on the boot a sleeve portion and a flange surrounding thesleeve portion at one end;

clamping the sleeve portion of the boot to the member;

sealing the flange of the boot to the liner at the hole;

and providing in the boot an expandable portion allowing longitudinalmovement downward of the flange relative to an upper part of the sleeveof the boot such that the expandable portion allows the ground on whichthe liner lies to move downwardly relative to the member afterattachment of the liner to the boot and the upper part of the sleeve ofthe boot to the member.

The method described above is primarily for use where the liquidcontainer is a tank. However the method may also be used for processpipe penetrations (i.e. something other than pilings) that come upthrough the floor of the cell, or through the side wall. Thus there maynot be a tank present.

Also, while the containment wall will generally be a steel wall whichare the high use application, this may also be used with other forms ofsecondary containment such as dirt berms which are also lined andsubject to the same conditions.

Preferably the boot has a portion at the flange which is of largertransverse dimension than at the upper part of the sleeve so as to allowthe flange to move horizontally with the liner relative to the member.

Preferably the boot is connected to the flange at the bottom part of theexpansion portion.

Preferably the expansion portion is frusto-conical from a lower end ofthe upper part of the sleeve to the flange.

Preferably the expansion portion can un-fold from a position in whichthe lower end of the upper part of the sleeve lies in a plane of theflange to a position in which the lower end is raised.

Preferably the expansion portion is frusto-conical with a cone angle inthe range 45 to 60 degrees.

Preferably the sleeve above the expansion portion is frusto-conical atan angle less than that of the expansion portion.

Preferably the expansion portion includes an accordion wall between thelower end of the sleeve portion and the flange.

Preferably the sleeve portion is attached to the member by a surroundingclamp and is sealed to the member by a sealing grout.

The present inventors have found that the currently available pipe bootsprovide no provision for vertical expansion or collapsing. As a result,as the ground can settle after installation the boots will tear awayfrom the pipe, resulting in loss of containment. This requires repair orreplacement. As the space underneath the tank is often very restricted,this can prove difficult, or even impossible without costly remedialactions.

Also, the liner itself is subject to expansion and contraction due totemperature differentials. This results in lateral deflections. Theexisting pipe boots provide little protection against lateral movement,and tearing can result which again results in failure of thecontainment.

Thus in the present arrangement, in addition to the clamping area andthe flange, which are incorporated into the existing pipe boot, there isalso an expansion component incorporated between the two to allow forvertical and lateral expansion and contraction.

As with the current pipe boots, there are a variety of sizes to match avariety of pipe diameters.

The collapsible pipe boots are manufactured, and shipped, in theexpanded configuration (as this lends itself to traditionalmanufacturing methods and shipping efficiencies).

Before installation the pipe boots are configured to their collapsedposition by pushing down from the top.

In the collapsed position, sufficient clamping area remains exposedabove the collapsed area to facilitate ease of banding and caulking(which remain consistent with current methods)

The interaction of the flange to the liner remains consistent withcurrent processes in that the liner is welded to the boot flange.

Once installed, the boot is free to expand vertically as required forheight differential caused by ground settlement, or other.

In addition, the boot provides for a certain amount of lateralflexibility as well to compensate for expansion and contraction of theliner material.

While a frusto-conical expansion section which simply folds at aposition part way along its length is preferred as being simple tomanufacture and ship, alternative different means of providing expansionand contraction are possible, such as a bellows arrangement, anaccordion arrangement, etc. The concept herein is the verticalexpansion.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the invention will now be described in conjunctionwith the accompanying drawings in which:

FIG. 1 is a vertical cross sectional view through a secondarycontainment system and method showing a pipe boot according to thepresent invention.

FIG. 2 is a cross sectional view on an enlarged scale of the pipe bootof FIG. 1.

FIG. 3 is a cross sectional view on an enlarged scale of an alternativeform of the pipe boot to be used in the method of FIG. 1.

In the drawings like characters of reference indicate correspondingparts in the different figures.

DETAILED DESCRIPTION

FIG. 1 shows schematically a secondary containment system for liquidescaping from a tank 10. The containment system comprises a containmentwall 11 supported on a base plate 12 and maintained upright by a brace13, A liner 14 extends across the ground underneath the tank and isfastened to the wall so that an edge of the liner runs up the insidesurface of the wall and attached to the wall at a suitable heightrelative thereto.

The construction of the wall and liner is shown only schematically sincethese can vary in arrangement and location in accordance with manydesigns available to a person skilled in the art.

In the arrangement shown the tank 10 is mounted on a piling or post 15which engages into the ground 16 beneath the liner 14. The post thusextends from below the ground to the tank at a position above the groundso that the liner must be perforated to surround the post.

The liner is commonly fabricated from sheets so that an opening can beformed by cutting and by welding or sealing the edges together to formthe required dimensions and shape of the liner. Preferably, the linermay be applied while the piles are exposed from the ground and beforethe tank is attached so that a simple hole can be cut in the liner andplaced over the pile.

The hole is cut of course slightly larger than the pile so as to fitreadily over the pile or around the pile.

In order to seal the liner to the pile 15, there is provided a pipe bootgenerally indicated at 20. The pipe boot 20 comprises a sleeve portion21 and a flange 22. The sleeve portion 21 is attached to the outsidesurface of the pile 15 and the flange 22 is welded to the edge 14A ofthe hole in the liner 14. The sleeve portion is attached to the pile bya ring or bead of grout 32 located between the top of the sleeve portionand the pile. Around the sleeve portion is attached a clamping band 23of conventional nature which is tightened to fasten around the sleeveportion and to squeeze it down onto the ring of grout to provide asealing action.

The pipe boot further includes an expansion portion 25 of the pipe bootlocated between the sleeve portion 21 and the flange 22. Theconstruction of the pipe boot is shown in more detail in FIG. 2. Thesleeve portion 21 extends from an upper end 26 to a lower end 27. Thesleeve portion is slightly conical so that the upper end 26 closelysurrounds the outside surface of the piling while the lower end 27 isspaced further away from the piling. The purpose of the conical sleeveis to cover a range of pipe diameters, and wall thicknesses, which mightresult in a variability in pipe ODs where the sleeve can be cut to theappropriate diameter.

Between the flange 22 and the lower end 27 of the sleeve portion isprovided the expansion portion 25. In the arrangement shown thiscomprises a simple frusto-conical section extending downwardly andoutwardly from the lower end 27 of the sleeve portion to the inner edge22A of the flange. This conical section has a cone angle lying in therange 45° to 60° which allows it to fold into the construction shown indoffed line indicated at 25A so that the lower end 27 is moved to thepoint indicated at 27A and is provided a fold indicated at 28. Thus thesleeve portion 21 is moved into a retracted or collapsed position byfolding around two annular fold lines indicated at 28 and 28 A. Thematerial may be weakened at these locations to provide an effectivefolding action at those locations. However this is not necessary. Thematerial may be arranged so that the collapsed position defines a stableposition of the structure in which it holds its position until pulledout of that position in the expansion direction.

In the collapsed position the upper end 26 of the sleeve portion islocated above the height of the fold line 28 so that sufficient of thesleeve portion is available to receive the band 23 and the layer ofcaulking 32. The movement of the pipe boot between the expanded andcollapsed conditions is of the order of 6 to 10 inches and can begreater in specific arrangements. In the collapsed position theexpansion portion defines a stable position of the structure in which itholds its position until pulled out of that position in the expansiondirection. In the collapsed position a component of the expansionportion, that is the bottom fold line 28A is in a common plane with theflange to locate the collapsed position when the flange is located onthe ground for attachment to the liner.

The pipe boot is transported in the expanded position but when attachedto the pile is moved to the collapsed position by pushing down on theupper edge 26. This causes the folding action that pushes the upper edge26 to the lowered position where it is attached to the piling. Theflange 22 is then welded using conventional techniques or is sealedusing an adhesive or heat sealing to the edge of the liner.

In use, after a period of time, the ground surface surrounding the pilecan often collapse or subside by distance as much as 6 to 10 inches andusing the pipe boot described above, this downward movement whichcarries also the liner in a downward direction is accommodated bypulling on the expansion portion which then allows the construction tounfold to the expanded position shown in full line in FIG. 2.

It will also be noted that the expansion portion 25 is frusto-conical sothat where it meets the flange 22A is at a significantly greaterdiameter than the lower end 27 of the sleeve portion. In the eventtherefore that there is expansion or contraction of the liner in asideways direction tending to pull the flange in one direction or theother away from the piling, the conical shape and the larger diameter ofthe flange allows the flange to be pulled away from the piling by theliner movement without acting to tear the pipe boot or to tear the pipeboot away from the liner.

In FIG. 3 is shown an alternative arrangement which has a sleeve portion21 similar to that previously described but includes as an expansionportion between sleeve portion and the flange 22 as an accordion shapegenerally indicated at 35. The accordion shape allows simple compressionof the sleeve portion downwardly by compressing the accordion folds andallows the arrangement to be pulled upwardly in the event that expansionis required.

This arrangement is less satisfactory in view of the greater difficultyof manufacture and the greater difficulty of placing the pipe boots instacked position for transportation. It will be noted that thearrangement of FIG. 1 and FIG. 2 allows the pipe boot to simply bestacked one on the next in the expanded condition.

It has been determined that the folding action which takes place betweenthe expanded and collapsed condition shown in FIGS. 1 and 2 can becarried out while accommodating the forces involved without tearing theliner and also bearing in mind the thickness and rigidity of the pipeboot which is desirable to match that of the liner.

The liner thicknesses may vary with application. A liner of 30 mil isthe current minimum specified by Alberta regulations for secondarycontainment applications. However a liner of 40 mil seems to be thestandard. Since there is a thinning of material during the bootmanufacturing process and for cost advantage it is preferable tomaintain the minimum 30 mil for standard product offerings.

This thickness and material provides a pipe boot which is relativelystiff but can still fold to take up the expanded and collapsed positionsshown in FIGS. 1 and 2.

Since various modifications can be made in my invention as herein abovedescribed, and many apparently widely different embodiments of same madewithin the spirit and scope of the claims without departure from suchspirit and scope, it is intended that all matter contained in theaccompanying specification shall be interpreted as illustrative only andnot in a limiting sense.

1. A method for secondary containment of a liquid in a liquid container,where the liquid container is surrounded by a containment wall and wherethe liquid container has connected thereto at least one member whichextends from the liquid container downwardly into the ground within thecontainment wall, the method comprising: providing a liner covering theground within the containment wall and extending from the containmentwall at least partly under the liquid container; forming in the liner ahole surrounding the member; providing a boot which surrounds the memberand connects from the member to the material of the liner surroundingthe hole; providing on the boot a sleeve portion and a flangesurrounding the sleeve portion at one end; clamping the sleeve portionof the boot to the member; sealing the flange of the boot to the linerat the hole; and providing in the boot an expandable portion allowinglongitudinal movement downward of the flange relative to an upper partof the sleeve of the boot such that the expandable portion allows theground on which the liner lies to move downwardly relative to the memberafter attachment of the liner to the boot and the upper part of thesleeve of the boot to the member.
 2. The method according to claim 1wherein the boot has a portion at the flange which is of largertransverse dimension than at the upper part of the sleeve so as to allowthe flange to move horizontally with the liner relative to the member,3. The method according to claim 2 wherein the boot is connected to theflange at the bottom part of the expansion portion.
 4. The methodaccording to claim 1 wherein the expansion portion is frusto-conicalfrom a lower end of the upper part of the sleeve to the flange.
 5. Themethod according to claim 4 wherein the expansion portion can un-foldfrom a position in which the lower end of the upper part of the sleeveis in a common plane with the flange to a position in which the lowerend is raised.
 6. The method according to claim 1 wherein the expansionportion is frusto-conical with a cone angle in the range 45 to 60degrees.
 7. The method according to claim 6 wherein the sleeve above theexpansion portion is frusto-conical at an angle less than that of theexpansion portion.
 8. The method according to claim 1 wherein theexpansion portion includes an accordion wall between the lower end ofthe sleeve portion and the flange.
 9. The method according to claim 1wherein the sleeve portion is attached to the member by a surroundingclamp and is sealed to the member by a sealing grout.
 10. The methodaccording to claim 1 wherein in the collapsed position an upper end ofthe sleeve portion is located above the height of the expansion portionso that sufficient of the sleeve portion is available to attach to themember.
 11. The method according to claim 1 wherein the collapsedposition defines a stable position of the structure in which it holdsits position until pulled out of that position in the expansiondirection.
 12. The method according to claim 1 wherein in the collapsedposition a component of the expansion portion is in a common plane withthe flange to locate the collapsed position.